The novel coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One of the pathologies associated with COVID-19 is pneumonia that quickly leads to acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) and ultimately patient death. Recent studies suggested a critical role of the NLRP3 inflammasome, a multiprotein platform that tightly regulates the innate immune response, in the development of ARDS/ALI in COVID-19. Dysregulation of the NLRP3 inflammasome is responsible for the excessive production of pro-inflammatory interleukin (IL)-1? and IL-18, whch is involved in the uncontrolled inflammatory responses and cytokine storm. Therefore, development of NLRP3 inhibitors (NLRP3is) represents a novel approach to mitigating ARDS/ALI in COVID-19 patients. Recently, we developed novel small molecule NLRP3is that blocks the assembly and activation of the NLRP3 inflammasome, resulting in inhibition of IL-1? production both in vitro and in vivo. Studies in animal models of neurodegenerative disorders demonstrated target engagement and in vivo efficacy, thus providing proof-of-concept for further developing NLRP3is as therapeutics. Notably, our studies in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis in which excessive inflammation is one of the prominent pathologies, showed that the lead inhibitor reduced the severity of EAE both preventively and therapeutically. Treatment with this lead compound also substantially reduced the type 17-helper T (Th17) cells that produce IL-17, indicating its potential in restraining uncontrolled inflammation. The central hypothesis of this proposal is that aberrant activation of NLRP3 inflammasome contributes to the induction of cytokine storm and development of ARDS/ALI in COVID- 19, and its pharmacological inhibition with NLRP3is will prevent and reduce ARDS. With the current R01 support (R01AG058673), we have successfully developed selective NLRP3is from novel chemical scaffolds and identified lead compounds with improved inhibitory potency and druggability. We also identified compounds as non-selective NLRP3is to reduce the production of multiple pro-inflammatory cytokines including IL-1?, IL-6 and TNF-alpha. The goal of this supplement project is to test selective and non-selective NLRP3is as potential treatments for ARDS in COVID-19. Two specific aims are proposed in this application. In Aim 1, analogs based on the newly identified chemical scaffolds will be designed and synthesized to identify candidates for in vivo studies. In Aim 2, the top candidate inhibitors will be studied to confirm the therapeutic efficacy to mitigate lung injury in a mouse model of ARDS. The proposed research is highly significant because successful development of novel NLRP3is may provide promising candidates with translational potential for clinical management of COVID-19.